Petroleum oil refining process



Patented Oct. 21, 1952 PETROLEUM OIL REFINING PROCESS Byron M.Vanderbilt and Anthony H. Gleason,

Westfield, N. J., assignors to Standard Oil Development Company, acorporation of Delaware No Drawing. Application July 28, 1949,

; Serial No.107,383

This invention relates to an improved: process for refining mineraloils. The process is directed to the removal of gum forming substances,to the sweetening of the oils treated, and to the color improvement ofthese oils. In accordance with this invention treating agents consistingof.

finely divided metallic sodium'and a secondary or tertiary alcohol areutilized as refining agents.

At the present time a great many refining processes are known forimproving the quality of mineral oils. These processes are generallydirected to improving one or more characteristics of the oil so as toproduce superior oils. For example, in the refining of gasolines, it isfrequently desirable, or necessary, to improve the odor of the gasolineby sweetening the gasoline so as to remove malodorous mercaptans, or soasto convert them tocompounds which do not have an objectionable odor.Again refining processes are used to increase the resistance of the oilto oxidation, decreasing the tendency of the oil to form objectionablegum deposits in storage and transit. The process of this invention is,therefore, directed to this general field in which petroleum oils arerefined in a manner to improve the characteristics of these oils.

While the process of this invention is of general application to mineraloils, or petroleum oils generally, it will be described with particularreference to the refining of cracked gasolines as this ispresently'contemplated to be the most important application of thisprocess. Asa refining process for gasolines, a major objective of thisprocess is to provide a stable and a sweet gasoline. In the past it hasbeen the practice to achieve this by two treating processes, i. e'.treating with sulfuric acid and sodium plumbite. A further object ofthis invention is to decrease the oxidation instability of gasolines; Aswill be apparent from the ensuing description, these and otherobjectives are attained by the single step refining process describedherein.

In its broadest scope this invention concerns the treatment of a mineraloil with sodium, potassium, or lithium in combination with a suitableactivator. The activator may consist of a mono or polyhydric alcoholalthough it i presently felt that monohydric alcohols are more suitable.A particularly effective refining agent (or agents) consists of fineparticles of sodium together with a minor proportion of a secondary ortertiary alcohol. Inthe description which follows, referones willparticularly be made to this specific refining agent althoughit is to beunderstood that potassium or lithium may be used in place 7 Claims. (01.196-24) .As indicated the novel refining agent of this inventionconsists of a major proportion of finely divided sodium and a minorproportion of a secondary or tertiary alcohol. It is believed that thealcohol probably reacts with sodium to form a sodium alcoholate. If thisis true the refining agent may be said to be a sodium alcoholate formedin the presence of an excess of sodium so that free sodium is presentwith the alcoholate. In this connection, however, it, is "significantthat the desired refining results cannot be obtained by utilization ofeither sodium alone or sodium alcoholate alone. Again, the mostdesirable refining results can not be obtained by forming thesodium-alcohol reaction products, believed to be primarily thealcoholate, in the absence of hydro-- carbons. While the exact nature ofthis efiect is 1 cracked gasolines.

not yet thoroughly understood, it appears that a Furthermore, it idesirable that the secondary,

or tertiary alcohol used have less than about '7 carbon atoms since thereaction products formed with a greater number of carbon atoms are sum--ciently soluble to necessitate distillation of the oil after treating.Hence the preferred alcohols are secondary alcohols having from 3 to 6carbon atoms, and tertiary alcohols having from 4 to 6 carbon atoms. Ofthese the preferred alcohols are iso-propyl alcohol, and secondary andtertiary butyl alcohols.

The sodium utilized in this novel refining process is preferablysupplied as a fine dispersion of sodium in a suitable vehicle such as ahydrocarbon oil. Such a dispersion may be obtained by adding sodium tothe vehicle and by then heating the mixture of sodium and the vehicle toa temperature above, the melting point of the sodium. Uponthen agitatingthe melted sodium, and the vehicle, a fine dispersion of the sodium maybe obtained. The vehicle may consist of virtually any hydrocarbon oilbut is preferably a high boiling gasoline fraction substantially free ofolefinic materials. It is desirable to utilize a high speed agitator, ahomogenizer, a colloid mill or similar means for thoroughly dispersingthe molten sodium in the vehicle. In this connec-. tion it has beenfound critical that the sodium have a particle size of less than about50' microns in diameter. Further it has been found highly desirable thatthe sodium have diameters not greater than about 30 microns andpreferably below an average of microns.

This dispersion of sodium in a hydrocarbon oil can then be added to theoil to be refined in combination with suitable quantities of a suitablealcohol. Thereafter the desired refining may be accomplished by heatingthe mineral oil in the presence of the indicated refining agent for aperiod of about 10 minutes to two hours, at a pressure suitable to holdthe mineral oil in liquid phase, and at temperatures of 70 to 160 C., orhigher. Atthe conclusion of the refining period the mixture is cooled,if necessary, to

a temperature below about 100 F. and the spent refining agent, togetherwith any unreacted sodium and constituents removed from the oil may besettled from therefined oil in the form of a sludge. The remaining oilwill be found to be suitably refined without necessity for re- 7 runningor other treating steps. In order to more clearly disclose the nature ofthis invention, consideration will be directed to typical examplesembodying and defining the process of this invention.

EXAMPLE I A crude gasoline boiling in the range of 170 to 400 E. whichwas obtained by the thermal cracking of a reduced crude oil wascontacted for one hour, at 70 0., with 1% by weight of finely dividedsodium. The sodium was added to the gasoline in the form of a dispersionin straight run kerosene, in weight proportions of about 1 to l, andhaving a particle diameter of about 30 microns. During the hour ofcontact, internal agitation was provided to thoroughly mix the sodiumand gasoline. After the treating period the mixture was cooled to roomtemperature, a sludge and unreacted sodium was removed from the gasolineby filtration. The treated gasoline comprising the filtrate was thentested by a variety of tests as indicated in Table I. For comparativepurposes, in Table I, the results of these same tests are given on acontrol sample of the gasoline employed.

D Indigates oxidation stability in minutes according to ASIM test 525-42 Indicates the active oxygen content of the gasoline.

3 Indicates gum content in mg./l00 cc. obtained by evaporating thegasoline at 212 F. in a copper dish.

Indicates presence or absence of mercaptans by utilization of sodiumplumbite solution and a trace of free sulfur. If no color change occursmercaptans are absent and the gasoline is said to pass."

6 Indicates engine cleanliness characteristics of gasoline. This testutilizes the coupling reaction which takes place between diazotiscdp-nitro aniline and certain unsaturated compounds (which cause enginefouling) to form a colored compound. Intensity of color formed after agiven time interval is taken as an index of the deposit formingcompounds present. In running the test the fraction of the sampleboiling over 275 F.'and purified by treatment with dilute acid andalkali and steam distillation to 3% bottoms is used. A known quantity ofthis fraction is added to a solution of p-nitroaniline diazoniumfiuoborate (NO2CGH4NZNBF4) in acetone and the optical density measuredat intervals in a Hellige-Diller emission photometer. The opticaldensity is plotted against time and the value after minutes read fromthe curve. The optical density multiplied by the ratio of the fractionboiling over 275 F. to the whole sample gives the diazonium depositfactor.

It will be noted from Table I, that the sodium treatment of the gasolinedid not markedly improve the quality of the gasoline. The ASTM 4break-down test indicated that the sodium treat ment was actuallyineffective in increasing the oxidation stability of the gasoline whichis borne out also by theCopper Dish gum test which indicated that agreater amount of gum was formed after the gasoline had been subjectedto the sodium treatment. The sodium treatment was effective in causingthe gasoline to pass the Doctor test, but was only slightly effective inincreasing the quality of the gasoline as indicated by the diazoniumdeposit factor.

EXAMPLE II The gasoline treated in Example I, was treated in the samemanner except that 5% of the stoichiometric amount of isopropyl alcoholrequired to react with the sodium was added to the gasoline prior to theaddition of the finely divided sodium. The isopropyl alcohol employedwas of 99% purity. The results of this test are again indicated in TableI, identified as Example II. It will be noted that as indicated by thesedata, the ASTM break-down test and the Copper Dish gum test indicated amaterial improvement in the oxidation characteristics of the gasoline,while the Doctor test showed that mercaptans were removed, and thediazonium deposit factor of the gasoline indicated marked improvement inthe engine cleanliness characteristics of the gasoline. A comparison ofthe results obtained by the treating steps of Example II, as compared toExample I, indicates a marked advantage for the process in which theisopropyl alcohol WaS present.

EXAMPLE III The experiment performed in Example II was repeated, exceptthat after one-half of the onehour contact time an additional 5% of thestoichiometric quantity of isopropyl alcohol was added. In this example,therefore, 10% of the molar quantity of the isopropyl alcohol, based onthe sodium was utilized. Again, the results of this test are indicatedin Table I, identified as Example III. It will be noted from these datathat the improvement in the gasoline characteristics, as indicated byeach of the tests, was materially better than in either of the previoustreating runs. Again, therefore, in comparing Examples I, II and III,the importance of having a significant amount of alcohol present isborne out, indicating that a molar proportion of about 10% of alcoholbased on total sodium is desirable.

Furtherexperiments were conducted, particularly directed to anevaluation of suitable alcohols for use in the process of thisinvention. These experiments will be indicated below as Examples IV toIX inclusive, the results of which are summarized in Table II appendedherewith. In these tests the gasoline treated was obtained by thethermal cracking of a reduced crude oil stock and had a boiling range ofabout F. to 400 F. The gasoline was characterized by the inspectionsgiven in Table II, showing the ASTM break-down time, Copper Dish gumnum-- ber; peroxide number; the Doctor test; the total sulfur, and thediazonium deposit factor of the gasoline. In each of the treatingExamples V to IX, 10 molar percent of various alcohols were used basedon the quantity of sodium employed. The amount of sodium used was 0.75%based on the gasoline treated and it was added in the form of adispersion in a fraction of virgin crude oil having a boiling point of360 to 480 F. The

sodium. particles had an a erage=- diameter of about 30microns, and werepresentin the dispersion in a weight percent of "about 50%. In each ofthe tests conducted, the alcohol was mixed in the gasoline prior totheadditionof thesodium dispersion. After a contacttime of i one hour,at a temperature of 90 0., while employing mild agitation, the treatedgasoline was separated from the sludge and unreactedsodium by filtrationat room temperature. Results of the test are indicated in Table II. i

Table II AS'IM Copper Peroif- Ex Alcohol Doctor Total .1 n Break- Dishide No. Used down Gum N0 Test 1 Sulfui 215 13 'ojs DNP. 0.108 340 "4.50.2 305 3 0.2 r 240 15.5 0.2 VII. Isopr0pyl.- 025 7.5 0.1 VIII.Scc-Butyll" 720 2.5 0.1 n'l3utyl 290 19.5 0.3

i As shown by. Example IV, identified in Table II, when using sodiumalone as the refining agent in the absence of an alcohol, a relativelysmall improvement of the gasoline was obtained in regard to oxidationstability as indicated by the ASTM break-down test. A furthercharacteristic of Example IV, was the poor sodium dispersion which wasmaintained during the contacting, resulting in the formation of largesodium agglomerates at the end of the treating period.

Example V, utilizing. methyl alcohol together with-sodium, wasalsocharacterized by poor sodidispersion, and again did not result inmate rially improving the ASTM break-down characteristics of thegasoline. i

Example 'VI, utilizing ethyl. alcohol, indicated that an excellentsodiumdispersion could be obtained using the ethyl alcohol, but as indicatedby the data, did not result in materially improvingthe quality ofthegasoline. Thus, as shown by the ASTM break-down data, the Copper Dishgum test, and the total sulfur content, the refining of the gasolinewith sodium in the presence of ethyl alcohol did not substantiallyimprove the gasoline. 1

Examples VII and VIII, utilizing isopropyl alcohol and secondarybutylalcohol respectively, resulted in the formation of excellent sodiumdispersions, and as indicated by the'data, served to materially improveeach of the characteristics of the gasoline as determined by the testsindi cated. i

Finally, Example IX of Table II, utilizing normal butyl alcohol, eventhough a good dispersion was obtained, again demonstrated that therefining results utilizing a primary alcohol are not good even though asecondary alcohol of like molecular weight'was quite effective. 1 Ihedata of Table II substantiate the conclusion that when no alcohol isemployed, a poor sodium-sludge dispersion is obtained which is also thecase when using methyl alcohol. Fur then the primary alcohols tested,methyl, ethyl, and normal butyl alcohol appear to offer no ad'- vantagein sodium refiningover the case in which no alcohol whatever is used.This result is particularly surprising in view of the fact that'ethylialcohol results in the formation of an excellent sodiumrdispersionwFinally the data demonstrate ithat 1 the secondary alcohols; such. asisopropyl alcohol and secondary butyl alcoholw'ar e highly 5,7 5

of combined sodium).

eflective inenhancing the deflning" effects or an Restating theconclusions drawn from the data of Table II, itis particularlysignificant that the function of the alcohol employed is not simply toprovide a better sodium dispersion. The data in dicate the possibilitythat the sodium and alcohol may enter into some complex with olefins, orother-hydrocarbons present to form a more ac tive refining catalyst.This conclusion is strengthened by the data obtained in. Examples X andXI, following.

, EXAMPLE X 400 grams of a gasoline obtained in a thermal crackingoperation, having a boiling range of about to 400 F., was treated with3.6 grams of sodium (0.9 by weight) and 1.53 grams of finely groundsodium isopropylate (equivalent to 0.1% The sodium isopropylate wasprepared by adding metallic sodium to an excess of pure isopropylalcohol and isolating, drying the grinding to a fine powder thealcoholate obtained. Thus, 10% of the total sodium present was presentin the form of the sodium isopro pylate. The dispersion of sodiumparticles had diametersof 2 to 5 microns and the alcoholate passedthrough a LO-mesh screen. The mixture with gasoline was heated withagitation for one hour at 90 C. after which the gasoline was sepa ratedby filtration. The results of this test are indicated in Table IIIbelow. 7

- Tdble I11 ASTM new Break- Percent? nium Peroxide f down Sulfur DepositNo. No Test .:,;I Factor Untreated y i Gasoline... 1 1 .146 55 1.4 i 264Example X. in; i :12 i 64 .6 =94 Example XL 365 .127 39 .4 l0

EXAMPLE XI For comparative purposes with Example X, a refining operationwas conducted utilizing the identical conditions as in Example X,.except that the isopropyl alcohol was first added to-the gasoline toberefined prior to the addition of the sodium, that is, the sodiumisopropylate was not extraneously formed inthis example, but was formedin situ (if at all) in the presence of the gasoline to be refined. Theresults of this experimen-tare also indicated in Table III. It will benoted from a comparison of Examples and XI, that materially betterrefining results were obtained according. tothe procedure of Example XI,

inwhich the sodium galcoholate was formed, in

situ rather than being preformed; Thus the de posit factor, peroxidenumber and copper gum number of the gasoline refined according to thesteps of Example XI are materially better than those obtained by theprocedure of Example X.

i As a still further example of this invention a lcrackedthermal naphthawas treated with a dis- ,persion of sodium together with tertiary butylalcohol. In this example, 400 grams of the cracked thermal naphtha weremixed with 1.3 grams of tertiary butyl alcohol and 4 grams of sodiumintroduced in the formof asodium dispersion in kerosene containing 45%sodiumfby weight. These quantities provideda total sodium content of 1%along with 10 molar percent of the .alcohol-based.. on. the. o ium A i ton w maintained ior. .pne. bonnet a. tem er tu i 19 90 C. The sludge,and unreacted sodium were removed by filtration, after coolingbelow 100F., and the treated gasoline filtrate was compared with the untreatedstock according to the tests indicated in Table IV. It will be observedin this table that the refining of the gasoline with the sodium, in thepresence of the tertiary butyl alcohol resulted in a substantialimprovement of the gasoline quality as indicated by each of the tests. 1Table IV ASTM Breakf Peroxide Doctor Deposit down Gum No. Test FactorTest I NoTreat mo 27 1.4 DNP-.. 5e ExempleXII 900 1.5 0.3 Passes.-- 18.5

EXAMPLE XIII A one percent solution of thiophene was prepared in purepara xylene. Four hundred grams of this solution was contacted for onehour at 90 C. with 3.3 grams of colloidally dispersed sodium having anaverage diameter of five microns. After the contact period the sludgewas removed by filtering at room temperature and the filtrate analyzedfor sulfur content.

' EXAMPLE XIV Example XIII was repeated but modified in that 1.1 cc. ofisopropyl alcohol mole percent based on the sodium) was added tothiophene solution before adding the sodium dispersion.

EXAMPLE XV Example XIV was repeated but run at a temperature of 120 C.for one hour.

Indicated in Table V are the sulfur contents of the untreated andtreated xylene solutions.

Percent sulfur Untreated 0.248 Example XIII 0.250 Example XIV 0.134Example XV 0.103

-I I... v-..m-..-. n,"

ASTM

Copper Peroxide Doctor Total Break- 7 down Dish 0 Test Sulfur 235 63 0.4Passes." 0.111 Control 160' 204 1.4 DNP 0.146

It may be noted that while this example utilized a different controlstock than that for Examples V-IX, the results are in line.

. EXAMPLE XVII A sampleof naphtha from catalytic cracking I having-anboiling range of 325-437" F.

'butyl alcohol.

was treatedin various ways for the primary purpose of lowering its highsulfur content of 0.385%. Heavy catalytic cracked stocks are high insulfur which is difficult to lower even a small degree'by the usualmethods of refining such as sulfuric acid treating. Samples were treatedas follows:

(a) Treated with one percent of finely divided sodium 3-5 microns) alongwith 10 mole percent of isopropl alcoholfor one hour at C.

(b) As (a) butrun for two hours at 160 C.

(c) As (b) but using ten mole percent of tbutyl alcohol instead of theisopropyl alcohol.

(d) No metallic sodium was used but finely divided sodium isopropylate,equivalent to one percent sodium, was employed for one hour at 160 C.

Sulfur contents of the untreated and treated stocks were as follows:

Percent sulfur Untreated 0.385 Example XVII (a) 0.093 Example XVII (b)0.075 Example XVII (c) 0.072 Example XVII (d) 0.396

It may be observed that the isopropylate is entirely ineffective inlowering the sulfur content of the cracked naphtha whereas thesodiumalcohol combinations are quite effective as formerly indicated bythe examples utilizing thermally cracked gasoline.

In accordance wth these principles, therefore, the improved refiningprocess of this invention comprisesthe introduction of a fine dispersionof sodium to theoil to be refined, containing from 5 to 25 molar percent(based on sodium) of a secondaryor tertiary alcohol having from 3 to 6carbon atoms. The oil to be refined, the sodium, and the alcohol arethen agitated for a period of about one-half to two hours, at atemperature above about 70 C., and thereafter the refined oil isseparated from the sludge which has formed. Thus the refined oil may-berecovered by utilization of a settling Zone operative to permit thesludge to settle from the refined oil. Alternatively, a centrifuge, afilter, or other means may be used to separate the sludge from therefined oil. Oil entrained with, or adsorbed on the sludge may ifdesired be recovered by heating the sludge sufiiciently to drive out theadsorbed oil. Thereafter the sludge may be quenched with steam or waterto convert all reacted and unreacted sodium to sodium hydroxide. I

What is claimed is:

l. A process for improving the oxidation stability and enginecleanliness characteristics of a cracked gasoline comprising the stepsof separatelyadding to the gasoline about 1% by weight of a metalselected from the class consisting of sodium, potassium, and lithium andabout 5 to 25 molar percent of an alcohol based on the amount of thesaid metal, said alcohol being selected from the group consisting ofsecondary and tertiary alcohols of less than 7 carbon atoms, mixing thegasoline containing the metal and the alcohol for a period of tenminutes to two hours at a temperature above 70 C., and thereafterseparating the gasoline from sedimentatious material.

2. The process of claim 1 in which the alcohol is selected from theclass consisting of isopropyl alcohol, secondary butyl alcohol, andtertiary 3. The process of claim 1 in which the cracked gasoline is athermally cracked gasoline.

4. The process of claim 1 in which the cracked gasoline is acatalytically cracked gasoline.

5. The'process of claim 1 in which the said metal is added as adispersion in a hydrocarbon oil having particlesizes of less than about50 microns in diameter. l I

6. A process for improving the oxidation stability and for sweetening acracked gasoline comprising the steps of contacting said gasoline withan agent consisting of finely dispersed sodium and an alcohol selectedfrom the group consisting of secondary and tertiary alcohols having lessthan '7 carbon atoms to provide a proportion of about 1% by weight ofsodium and about 5 to 25 molar percent of the alcohol based on theamount of sodium, said contacting being carried out at a temperatureabove 70 C., and thereafter separating the treated gasoline fromsedimene tatious material. l

7. A process for improving the oxidation stability of a petroleum oilfraction in which the said oil is agitated with a minor quantityofsodium having a particular size less than 50 microns together with analcohol selected from 10 1 a I the group consisting of secondary andtertiary alcohols having less than 7 carbon atoms, said agitation beingconducted at a temperature above 70C. and said alcohol being present inthe. proportion of 5 to 25 molar percent based on the sodium employed.

BYRON M. VANDERBILT. ANTHONY H. GLEASON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Germany Sept. 2, 1924

1. A PROCESS FOR IMPROVING THE OXIDATION STABILITY AND ENGINECLEANLINESS CHARACTERISTICS OF A CRACKED GASOLINE COMPRISING THE STEPSOF SEPARATELY ADDING TO THE GASOLINE ABOUT 1% BY WEIGHT OF A METALSELECTED FROM THE CLASS CONSISTING OF SODIUM, POTASSIUM, AND LITHIUM ANDABOUT 5 TO 25 MOLAR PERCENT OF AN ALCOHOL BASED ON THE AMOUNT OF THESAID METAL, SAID ALCOHOL BEING SELECTED FROM THE GROUP CONSISTING OFSECONDARY AND TERTIARY ALCOHOLS OF LESS THAN 7 CARBON ATOMS, MIXING THEGASOLINE CONTAINING THE METAL AND THE ALCOHOL FOR A PERIOD OF TENMINUTES TO TWO HOURS AT A TEMPERATURE ABOVE 70* C., AND THEREAFTERSEPARATING THE GASOLINE FROM SEDIMETATIOUS MATERIAL.